Carbide contacts on homoepitaxial diamond films

We present experimental investigations of the structural and electrical pro perties of carbide contacts on homoepitaxial p-type diamond films in order to achieve Schottky diodes working at high temperatures with highly adhesiv e ohmic and Schottky contacts on diamond. For ohmic contacts, the reaction of molybdenum deposited by magnetron sputtering on homoepitaxial diamond la yer is studied through X-ray diffraction and Rutherford backscattering. The formation of hexagonal alpha-Mo2C begins at 700 degrees C. However, the re sidual oxygen is exodiffused only at 900 degrees C and for undoped diamond. Nevertheless, ohmic contacts are achieved after annealing at 900 degrees C , with a low contact resistivity at a boron concentration of 1.6 x 10(21) c m(-3). For Schottky contacts, the in-situ reaction under ultra-high vacuum between Er and a non-oxidized diamond surface begins at 700 degrees C. A po tential barrier height of 1.9 eV and a rectification ratio larger than 10(3 ) at 4 V at least up to 500 degrees C are obtained. In each case, coating l ayers intended to protect carbides against oxidation are assessed. (C) 1999 Elsevier Science S.A. All rights reserved.